Channel estimation with decision feedback

ABSTRACT

Systems, methods, and other embodiments associated with a method for estimating a channel between a wireless transmitter and a wireless receiver are described. According to one embodiment, a method includes receiving a signal that includes non-pilot data that is not known to a receiver of the signal; determining an estimated channel for the signal based, at least in part, on the non-pilot data; processing the signal based, at least in part, on the estimated channel to produce an equalized signal; and decoding the equalized signal to produce output data.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent disclosure claims the benefit of U.S. ProvisionalApplication No. 61/558,381 filed on Nov. 10, 2011, and U.S. ProvisionalApplication No. 61/650,175 filed on May 22, 2012 which are incorporatedherein by reference.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventor(s), to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

In a wireless network, a transmitter communicates with a receiver bytransmitting a signal to the receiver through a communication link orsignal path, also commonly referred to as a “channel”. The communicationlink or signal path between a transmitter and a receiver can berepresented by an effective channel, H. The effective channel representsthe combined effect of signal deflection due to obstacles (hills, walls,and so on), scattering, fading, and power decay due to the distancebetween a transmitter and a receiver. If either the transmitter orreceiver is in motion, the effective channel will be constantlychanging. Further, other obstacles in the signal path that affect thechannel may be moving. A conventional receiver is typically configuredwith an equalizer that attempts to undo effects on a signal caused bythe channel that carries the signal, therefore, the effective channel iscontinuously determined to allow effective communication even when oneor both of the transmitter and receiver are moving. The quality of theoutput data produced by the receiver is dependent upon accuratelydetermining the effective channel.

One way to estimate an instantaneous effective channel between areceiver and a transmitter is for the transmitter to transmit a knownpilot sequence. The pilot sequence can be inserted in predeterminedpositions in frames of data-carrying signals from the transmitter. Thereceiver determines the effective channel H based on characteristics ofthe pilot sequence. Accordingly, an equalizer can utilize the effectivechannel H to compensate for the effects of the channel on a receivedsignal. Channel estimation and equalization may be implemented in eitherthe time domain (e.g., pre FFT) or the frequency domain (e.g., postFFT). In orthogonal frequency domain multiplexed (OFDM) communicationsystems, channel estimation and equalization are performed in thefrequency domain.

SUMMARY

In general, in one aspect this specification discloses an apparatus forestimating a channel between a wireless transmitter and a wirelessreceiver. The apparatus includes a receiver configured to receive asignal transmitted through an effective channel, wherein the signalcomprises i) pilot data that is known to the receiver and ii) non-pilotdata that is not known to the receiver. The apparatus includes a channelestimation logic configured to determine an estimated channel thatestimates the effective channel based, at least in part, on thenon-pilot data in the signal. The apparatus includes an equalizerconfigured to process a signal based, at least in part, on the estimatedchannel to produce an equalized signal. The apparatus includes adecision logic configured to decode the equalized signal to produceoutput data.

In one embodiment, the signal is an orthogonal frequency divisionmultiplexed (OFDM) signal including data encoded in a plurality of datasubcarriers. The channel estimation logic is configured to determine asignal-to-noise ratio of data subcarriers in the output data, anddetermine the estimated channel based, at least in part, on thesignal-to-noise ratio of the data subcarriers in the output data.

In one embodiment, the channel estimation logic is configured todetermine the estimated channel based, at least in part, on the pilotdata in the signal.

In one embodiment, the channel estimation logic includes a first channelestimation logic configured to determine a first estimated channel basedon the pilot signal components. The equalizer is configured to processthe non-pilot data based, at least in part, on the first estimatedchannel to produce a first equalized signal. The decision logic isconfigured to decode the first equalized signal to produce first outputdata. The channel estimation logic includes a second channel estimationlogic configured to determine a second estimated channel for the signalbased, at least in part, on the first output data. The channelestimation logic determines the estimated channel based, at least inpart, on the first estimated channel and the second estimated channel.

In one embodiment, the signal is an OFDM signal including data encodedin a plurality of data subcarriers. The channel estimation logic furtherincludes an update logic configured to determine a signal-to-noise ratioof data subcarriers in the output data and determine the estimatedchannel by combining the first estimated channel and the secondestimated channel with respective weights based, at least in part, onthe signal-to-noise ratio.

In one embodiment, the apparatus also includes an interpolation logicconfigured to adapt an interpolation technique based, at least in part,on the first output data, wherein the interpolation logic adapts theinterpolation technique by i) modifying interpolation parameters, ii)selecting a different interpolation technique, or iii) both modifyinginterpolation parameters and selecting a different interpolationtechnique. The first channel estimation logic determines the firstestimated channel using the adapted interpolation technique.

In one embodiment, the signal is an OFDM signal including data encodedin a plurality of data subcarriers. The channel estimation logic furtherincludes an update logic configured to determine a signal-to-noise ratioof data subcarriers in the output data. The interpolation logic adaptsthe interpolation technique based, at least in part, on thesignal-to-noise ratio.

In general, in another aspect, this specification discloses a method forestimating a channel between a wireless transmitter and a wirelessreceiver. The method includes receiving a signal comprising non-pilotdata that is not known to a receiver of the signal; determining anestimated channel for the signal based, at least in part, on thenon-pilot data; processing the signal based, at least in part, on theestimated channel to produce an equalized signal; and decoding theequalized signal to produce output data.

In one embodiment, the signal is an OFDM signal including data encodedin a plurality of data subcarriers. Determining the estimated signalincludes determining a signal-to-noise ratio of data subcarriers in theoutput data and estimating the channel based, at least in part, on thesignal-to-noise ratio of the data subcarriers in the output data.

In one embodiment, the signal includes pilot data know to the receiverof the signal; and the estimating includes estimating the channel based,at least in part, on the pilot data in the signal.

In one embodiment, the determining includes determining a firstestimated channel based on the pilot data. The processing includesprocessing the non-pilot data based, at least in part, on the firstestimated channel to produce a first equalized signal. The decodingincludes decoding the first equalized signal to produce first outputdata. A second estimated channel is determined for the signal based, atleast in part, on the first output data. The estimated channel isdetermined based, at least in part, on the first estimated channel andthe second estimated channel.

In one embodiment, the signal is an OFDM signal comprising data encodedin a plurality of data subcarriers. The method includes determining asignal-to-noise ratio of data subcarriers in the first output data andestimating the channel by combining the first estimated channel and thesecond estimated channel with respective weights based, at least inpart, on the signal-to-noise ratio.

In one embodiment, estimating the first channel includes adapting aninterpolation technique based, at least in part, on the output data byi) modifying interpolation parameters, ii) selecting a differentinterpolation technique, or iii) both modifying interpolation parametersand selecting a different interpolation technique. The first estimatedchannel is determined using the adapted interpolation technique.

In one embodiment, the signal is an OFDM signal comprising data encodedin a plurality of data subcarriers. The method includes determining asignal-to-noise ratio of data subcarriers in the first output data andadapting the interpolation technique based, at least in part, on thesignal-to-noise ratio. The method includes determining the firstestimated channel using the adapted interpolation technique.

In general, in another aspect, this specification discloses a device forestimating a channel between a wireless transmitter and a wirelessreceiver. The device includes a receiver circuit configured to receivean OFDM signal comprising data encoded in a plurality of datasubcarriers. The device includes a channel estimation logic circuitconfigured to determine an estimated channel based, at least in part, onnon-pilot data in the signal. The device includes an equalizer circuitconfigured to process the signal based, at least in part, on theestimated channel to produce an equalized signal. The device includes adecision logic circuit configured to decode the equalized signal toproduce output data. The channel estimation logic circuit is configuredto determine a signal-to-noise ratio of data subcarriers in the outputdata and estimate the channel based, at least in part, on thesignal-to-noise ratio of the data subcarriers in the output data.

In one embodiment, the OFDM signal includes pilot data and non-pilotdata. The channel estimation logic circuit is configured to determinethe estimated channel based, at least in part, on the pilot data in thesignal.

In one embodiment, the channel estimation logic circuit is configured todetermine a first estimated channel based on the pilot signalcomponents. The equalizer circuit is configured to process the non-pilotsignal components based, at least in part, on the first estimatedchannel to produce a first equalized signal. The decision logic circuitis configured to decode the first equalized signal to produce firstoutput data. The channel estimation logic includes a second channelestimation logic configured to determine a second estimated channel forthe signal based, at least in part, on the first output data. Thechannel estimation logic determines the estimated channel based, atleast in part, on the first estimated channel and the second estimatedchannel.

In one embodiment, the channel estimation logic circuit is further isconfigured to determine respective signal-to-noise ratios of respectivedata subcarriers in the output data and determine the estimated channelfor respective data subcarriers by combining the first estimated channeland the second estimated channel with respective weights based, at leastin part, on the signal-to-noise ratio of the respective data subcarrier.

In one embodiment, the channel estimation logic circuit is further isconfigured to adapt an interpolation technique based, at least in part,on the output data by i) modifying interpolation parameters, ii)selecting a different interpolation technique, or iii) both modifyinginterpolation parameters and selecting a different interpolationtechnique. The channel estimation logic is configured to determine thefirst estimated channel using the selected interpolation technique.

In one embodiment, the channel estimation logic circuit is further isconfigured to adapt the interpolation technique based, at least in part,on the signal-to-noise ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate various systems, methods, andother embodiments of the disclosure. Illustrated element boundaries(e.g., boxes, groups of boxes, or other shapes) in the figures representone example of the boundaries. In some examples one element may bedesigned as multiple elements or multiple elements may be designed asone element. In some examples, an element shown as an internal componentof another element may be implemented as an external component and viceversa.

FIG. 1 illustrates one embodiment of an apparatus associated withchannel estimation with decision feedback.

FIG. 2 illustrates one embodiment of an apparatus associated withchannel estimation with decision feedback.

FIG. 3 illustrates one embodiment of an apparatus associated withchannel estimation with decision feedback.

FIG. 4 illustrates one embodiment of a method associated with channelestimation with decision feedback.

FIG. 5 illustrates one embodiment of a method associated with channelestimation with decision feedback.

FIG. 6 illustrates one embodiment of an integrated circuit associatedwith channel estimation with decision feedback.

DETAILED DESCRIPTION

Described herein are examples of systems, methods, and other embodimentsassociated with techniques for estimating a channel between atransmitter and a receiver in a wireless network. The systems, methods,and other embodiments described herein estimate a channel between atransmitter and receiver based, at least in part, on non-pilot signalcomponents of the signal corresponding to non-pilot data carried by thereceived signal. In one embodiment, after the non-pilot data, alsocalled decision data, is decoded from a received signal, the non-pilotdata is fed back to a channel estimation logic that determines aneffective channel. In one embodiment, the channel estimation logic alsouses pilot signals components in the received signal to determine theeffective channel. The channel estimation logic combines a firsteffective channel estimated based on pilot sequence components in thereceived signal with a second effective channel estimated based on thenon-pilot data to determine the effective channel.

FIG. 1 illustrates one embodiment of an orthogonal frequency divisionmultiplexed (OFDM) wireless receiver 100 configured to perform channelestimation in accordance with techniques described herein. The wireless100 receiver includes a channel estimation logic 110, an equalizer 120,and a decision logic 130. The channel estimation logic 110 estimates theeffective channel through which a received signal, {tilde over (Y)}(k),traveled from a transmitter. The estimated channel H(k) is an estimateof the effective channel between the transmitter and the receiver. Theestimated channel H(k) is provided to the equalizer 120, which equalizesthe signal {tilde over (Y)}(k) based on the estimated channel H(k) toremove the effects of the channel from the signal {tilde over (Y)}(k) toproduce an equalized signal {tilde over (X)}(k). The equalized signal{tilde over (X)}(k) is decoded by the decision logic 130 to produceoutput data {circumflex over (X)}(k) that corresponds to a most likelyvalue of the data encoded in the received signal {tilde over (Y)}(k).The output data {circumflex over (X)}(k) is fed back to the channelestimation logic 110. The channel estimation logic uses the output datato produce the estimated channel H(k). In this manner, the channelestimation logic 110 estimates the channel based, at least in part, onthe output data which is derived from non-pilot data, as opposed torelying solely on pilot components of the received signal {tilde over(Y)}(k).

FIG. 2 illustrates one embodiment of a receiver 200 that processes OFDMsignals using channel estimation with decision feedback. After beingconverted to the frequency domain by an FFT module, the received signal{tilde over (Y)}(k) may be conceptualized as shown in FIG. 2. Equallyspaced positions along the X (frequency) axis in the received signalcorresponds to different data subcarrier frequencies. Pilot signals Pare interleaved in the received signal at known subcarrier frequencies.Data encoded in the received signal is shown as x's within the receivedsignal.

A channel estimation logic 210 estimates a channel H(k) for use by anequalizer 220 in producing an equalized signal {tilde over (X)}(k). Theequalized signal is decoded by a decision logic 230 to produce outputdata {circumflex over (X)}(k). In OFDM signal processing that utilizesdigital modulation (e.g., quadrature amplitude modulation (QAM)), it isconvenient to express the output data as a constellation diagram likethe one shown in FIG. 2. The constellation diagram maps constellationvalues that are used in data subcarriers. The constellation values aremapped from cell words that are sets of parallel input data bits in thetransmitted signal. Until the received signal {tilde over (Y)}(k) isdecoded, it is not known in which particular constellation values thedata points (e.g., cell word) belong.

The constellation diagram is a two-dimensional scatter diagram in thecomplex plane at a given cell sampling instant. The circles representpossible constellation values that may be selected by a given modulationscheme as points in the complex plane. Each circle corresponds to oneconstellation value. The x's on the constellation diagram represent thereceived cell words. The decision logic 230 decodes the equalized signal{tilde over (X)}(k) by deciding to which constellation value each datacell word most likely belongs and constructing the output data{circumflex over (X)}(k) with the data values at the proper (e.g., mostlikely) data values at subcarrier frequencies. The distance between thedata points and their “assigned” circle is corresponds to a signal tonoise ratio (SNR) of the output data {circumflex over (X)}(k).

The channel estimation logic 210 includes an H1 estimation logic 212that estimates a first channel H1 based on the pilot components of thereceived signal. This estimation may be performed by interpolatingbetween the pilot signals as shown by the dashed line in received signal{tilde over (Y)}(k) to create an estimated channel for the data pointsubcarriers. A channel update logic 214 utilizes the first channel H1 tocreate the estimated channel H(k) that is provided to the equalizer 220.Initially, the equalizer 220 equalizes the received signal based only onH1 and the decision logic 230 decodes the signal to produce tentativeoutput data {circumflex over (X)}(k).

The tentative output data, which has been aligned with subcarrierfrequencies by the decision logic 230 is fed back to an H2 estimationlogic 216. The tentative output data {circumflex over (X)}(k) isillustrated in the frequency domain as the series of equally spacedarrows on the frequency axis. The pilot signals are shown in dotted linein {circumflex over (X)}(k). The H2 estimation logic uses the tentativeoutput data in the same manner as the H1 estimation logic uses the pilotsignals to estimate a second channel H2. A delay element is interposedbetween the decision logic 230 and the H2 estimation logic 216 as wellas between the FFT module and the H2 estimation logic 216 to align thereceived data {tilde over (Y)}(k) with the output data {circumflex over(X)}(k) that was derived from the received data.

The second channel H2 is provided to the channel update logic 214, whichdetermines the estimated channel H(k) based on both channels H1 and H2.The equalizer 220 uses the estimated channel H(k) to equalize the signaland the decision logic 230 decodes the equalized signal to produceoutput data. In this manner, the channel update logic 214 is able toleverage the additional information about the channel that can be foundusing the output data {circumflex over (X)}(k) thereby improving theestimated channel and, accordingly, the output data.

In one embodiment, the tentative output data {circumflex over (X)}(k) aswell as an SNR of the tentative output data is provided to the channelupdate logic 214. The channel update logic 214 utilizes the SNR and thetentative output data to determine relative weighting for H1 and H2. Forexample, if the SNR is high, more weight may be given to H2. Likewise,if the SNR is low, more weight may be given to H1. Weighting may be doneon a per carrier basis using the SNR for each carrier.

FIG. 3 illustrates one embodiment of a receiver 300 that processesorthogonal frequency division multiplexed (OFDM) signals using channelestimation with decision feedback and adaptive interpolation. A channelestimation logic 310 estimates a channel H(k) for use by an equalizer320 in producing equalized signal {tilde over (X)}(k). The equalizedsignal is decoded by a decision logic 330 to produce output data{circumflex over (X)}(k). The decision logic 330 decodes the output data{tilde over (X)}(k) by deciding to which constellation value each datacell most likely belongs and constructing the output data {circumflexover (X)}(k) with the data values at the proper (e.g., most likely) datavalues at subcarrier frequencies.

The channel estimation logic 310 includes an H1 estimation logic 312that estimates a first channel H1 based on the pilot components of thereceived signal. This estimation may be performed by interpolatingbetween the pilot signals as shown by the dashed line in {tilde over(Y)}(k) to create an estimated channel that covers the data points. Aninterpolation logic 318 selects an interpolation method (e.g., linear,spline, cubic, low pass filter) for use in estimating the first channelH1 based on the pilot components of the signal. A default interpolationtechnique may be selected (e.g., linear interpolation as shown in dashedline on the received signal {tilde over (Y)}(k) on the left). A channelupdate logic 314 utilizes the first channel H1 to create the estimatedchannel H(k) that is provided to the equalizer 320. Initially, theequalizer 320 equalizes the received signal based on H1 and the decisionlogic 330 decodes the signal to produce tentative output data{circumflex over (X)}(k).

The tentative output data, which has been aligned with subcarrierfrequencies by the decision logic 330 is fed back to an H2 estimationlogic 316. The H2 estimation logic 316 uses the tentative output data inthe same manner as the H1 estimation logic 312 uses the pilot signals toestimate a second channel H2. A delay element is interposed between thedecision logic 330 and the H2 estimation logic 316 as well as betweenthe FFT module and the H2 estimation logic 316 to align the receiveddata {tilde over (Y)}(k) with the output data {circumflex over (X)}(k)that was derived from the received data.

The tentative output data {circumflex over (X)}(k) is also fed back tothe interpolation logic 318. The interpolation logic 318 uses thetentative data to select an interpolation technique and/or adaptinterpolation parameters to best fit the tentative data. The H1 channelestimation logic uses the selected and/or adapted interpolationtechnique (e.g., the curved interpolation shown in dashed line on thereceived signal {tilde over (Y)}(k) on the right) to re-estimate thefirst channel H1. The re-estimated first channel H1 and the secondchannel H2 are provided to the channel update logic, which determinesthe estimated channel H(k) based on both H1 and H2. The equalizer 320uses the estimated channel H(k) to equalize the signal and the decisionlogic 330 decodes the equalized signal to produce output data. Inanother embodiment, parameters and coefficients used in the originalinterpolation technique are adapted to better fit the tentative data andthe interpolation operation is performed again. In this manner, thechannel update logic 314 is able to leverage the additional informationabout the channel that can be found using the output data {circumflexover (X)}(k) thereby improving both the estimated channel H1 and thechannel H(k) and, accordingly, the output data {circumflex over (X)}(k).

In one embodiment, the tentative output data {circumflex over (X)}(k) aswell as the SNR of the tentative output data is provide to the channelupdate logic 314. The channel update logic 314 utilizes the SNR and thetentative output data {circumflex over (X)}(k) to determine relativeweighting for H1 and H2. For example, if the SNR is high, more weightmay be given to H2. Likewise, if the SNR is low, more weight may begiven to H1. Weighting may be done on a per carrier basis using the SNRfor each carrier.

FIG. 4 illustrates one embodiment of a method 400 of estimating achannel with decision feedback. The method includes, at 410, receiving asignal that includes non-pilot signal components corresponding tonon-pilot data being carried by the signal. Non-pilot signal componentsinclude data that is encoded in the signal to be communicated by thesignal, as opposed to a prior known pilot signals that are encoded inthe signal to facilitate channel detection. At 420, the method includesestimating a channel for the signal based, at least in part, on thenon-pilot signal components. At 430, the method includes processing thenon-pilot signal components based, at least in part, on the channel toproduce an equalized signal. At 440, the method includes decoding theequalized signal to produce output data.

In one embodiment, the signal is an OFDM signal comprising data encodedin a plurality of data subcarriers. In this embodiment, the estimatingis performed by determining an SNR of data subcarriers in the outputdata and estimating the channel based, at least in part, on the SNR ofthe data subcarriers in the output data. Weighting may be done on a percarrier basis using the SNR for each carrier.

In one embodiment, the signal includes both pilot signal components andnon-pilot signal components. In this embodiment, the estimating isperformed by estimating the channel based, at least in part, on pilotsignal components in the signal as well as the non-pilot signalcomponents.

FIG. 5 illustrates one embodiment of a method 500 of estimating achannel with decision feedback. At 510, the method includes receiving asignal that includes non-pilot signal components corresponding tonon-pilot data being carried by the signal and pilot signal components.At 520, the method includes estimating a first channel based on thepilot signal components. At 530, the method includes equalizing thenon-pilot signal components based, at least in part, on the firstchannel to produce a first equalized signal. At 540, the method includesdecoding the first equalized signal to produce first output data. At550, the method includes estimating a second channel for the signalbased, at least in part, on the first output data. At 560, the methodincludes equalizing the non-pilot signal components based, at least inpart, on the first channel and the second channel to produce a secondequalized signal. At 570, the method includes decoding the secondequalized signal to produce second output data.

In one embodiment, the signal is an OFDM signal comprising data encodedin a plurality of data subcarriers. In this embodiment, the method alsoincludes determining an SNR of data subcarriers in the first output dataand estimating the channel by combining the first channel and the secondchannel with respective weights based, at least in part, on the SNR.

In one embodiment, the method includes estimating the first channel byselecting an interpolation technique based, at least in part, on thefirst output data and estimating the first channel using the selectedinterpolation technique. When the signal is an OFDM signal, the methodmay include determining an SNR of data subcarriers in the first outputdata and selecting the interpolation technique based, at least in part,on the SNR.

FIG. 6 illustrates one embodiment of an integrated circuit device 600configured to perform channel estimation with decision feedback. Thedevice 600 includes a receiver circuit 605, a channel estimation logiccircuit 610, an equalizer circuit 620, and a decision logic circuit 630.The receiver circuit 605 is configured to receive an OFDM signalcomprising data encoded in a plurality of data subcarriers and toperform an FFT operation on the signal to transform the signal into thefrequency domain. The equalizer circuit 620 is configured to process thesignal based, at least in part, on a channel to produce an equalizedsignal. The channel estimation logic circuit 610 is configured toestimate the channel based, at least in part, non-pilot signalcomponents corresponding to non-pilot data being carried by the signal.The decision logic circuit 630 is configured to decode the equalizedsignal to produce output data. The channel estimation logic circuit 610is further configured to determine a signal to noise ratio of datasubcarriers in the output data and estimate the channel based, at leastin part, on the SNR of the data subcarriers in the output data.

In one embodiment the receiver circuit 605 is configured to receive anOFDM signal that includes pilot signal components and non-pilot signalcomponents. The channel estimation logic circuit 610 is configured toestimate the channel based, at least in part, on pilot signal componentsin the signal.

The following includes definitions of selected terms employed herein.The definitions include various examples and/or forms of components thatfall within the scope of a term and that may be used for implementation.The examples are not intended to be limiting. Both singular and pluralforms of terms may be within the definitions.

References to “one embodiment”, “an embodiment”, “one example”, “anexample”, and so on, indicate that the embodiment(s) or example(s) sodescribed may include a particular feature, structure, characteristic,property, element, or limitation, but that not every embodiment orexample necessarily includes that particular feature, structure,characteristic, property, element or limitation. Furthermore, repeateduse of the phrase “in one embodiment” does not necessarily refer to thesame embodiment, though it may.

“Logic”, as used herein, includes but is not limited to hardware,firmware, instructions stored on a non-transitory computer-readablemedium, and/or combinations of each to perform a function(s) or anaction(s), and/or to cause a function or action from another logic,method, and/or system. Logic may include a microprocessor programmed toperform one or more of the disclosed functions/methods, a discrete logic(e.g., ASIC), an analog circuit, a digital circuit, a programmed logicdevice, a memory device containing instructions, and so on. Logic mayinclude one or more gates, combinations of gates, or other circuitcomponents. Where multiple logics are described, it may be possible toincorporate the multiple logics into one physical logic. Similarly,where a single logic is described, it may be possible to distribute thatsingle logic between multiple physical logics. One or more of thecomponents and functions described herein may be implemented using oneor more of the logic elements.

While for purposes of simplicity of explanation, illustratedmethodologies are shown and described as a series of blocks. Themethodologies are not limited by the order of the blocks as some blockscan occur in different orders and/or concurrently with other blocks fromthat shown and described. Moreover, less than all the illustrated blocksmay be used to implement an example methodology. Blocks may be combinedor separated into multiple components. Furthermore, additional and/oralternative methodologies can employ additional, not illustrated blocks.

To the extent that the term “includes” or “including” is employed in thedetailed description or the claims, it is intended to be inclusive in amanner similar to the term “comprising” as that term is interpreted whenemployed as a transitional word in a claim.

While example systems, methods, and so on have been illustrated bydescribing examples, and while the examples have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. It is, of course, not possible to describe every conceivablecombination of components or methodologies for purposes of describingthe systems, methods, and so on described herein. Therefore, thedisclosure is not limited to the specific details, the representativeapparatus, and illustrative examples shown and described. Thus, thisapplication is intended to embrace alterations, modifications, andvariations that fall within the scope of the appended claims.

What is claimed is:
 1. An apparatus, comprising: a receiver configuredto receive a signal transmitted through an effective channel, whereinthe signal comprises i) pilot data that is known to the receiver and ii)non-pilot data that is not known to the receiver; a channel estimationlogic configured to determine an estimated channel that estimates theeffective channel based, at least in part, on the non-pilot data in thesignal; an equalizer configured to process the signal based, at least inpart, on the estimated channel to produce an equalized signal; and adecision logic configured to decode the equalized signal to produceoutput data.
 2. The apparatus of claim 1, wherein: the signal is anorthogonal frequency division multiplexed (OFDM) signal comprising dataencoded in a plurality of data subcarriers; and the channel estimationlogic is configured to determine a signal-to-noise ratio of datasubcarriers in the output data, and determine the estimated channelbased, at least in part, on the signal-to-noise ratio of the datasubcarriers in the output data.
 3. The apparatus of claim 1, wherein thechannel estimation logic is configured to determine the estimatedchannel based, at least in part, on the pilot data in the signal.
 4. Theapparatus of claim 3, wherein: the channel estimation logic comprises afirst channel estimation logic configured to determine a first estimatedchannel based on the pilot data; the equalizer is configured to processthe non-pilot signal components based, at least in part, on the firstestimated channel to produce a first equalized signal; the decisionlogic is configured to decode the first equalized signal to producefirst output data; the channel estimation logic comprises a secondchannel estimation logic configured to determine a second estimatedchannel for the signal based, at least in part, on the first outputdata; and the channel estimation logic determines the estimated channelbased, at least in part, on the first estimated channel and the secondestimated channel.
 5. The apparatus of claim 4, wherein: the signal isan OFDM signal comprising data encoded in a plurality of datasubcarriers; and the channel estimation logic further comprises anupdate logic configured to: determine a signal-to-noise ratio of datasubcarriers in the output data; and determine the estimated channel bycombining the first estimated channel and the second estimated channelwith respective weights based, at least in part, on the signal-to-noiseratio.
 6. The apparatus of claim 4, further comprising: an interpolationlogic configured to adapt an interpolation technique based, at least inpart, on the first output data, wherein the interpolation logic adaptsthe interpolation technique by i) modifying interpolation parameters,ii) selecting a different interpolation technique, or iii) bothmodifying interpolation parameters and selecting a differentinterpolation technique; and wherein the first channel estimation logicdetermines the first estimated channel using the adapted interpolationtechnique.
 7. The apparatus of claim 6, wherein: the signal is an OFDMsignal comprising data encoded in a plurality of data subcarriers; thechannel estimation logic further comprises an update logic configured todetermine a signal-to-noise ratio of data subcarriers in the outputdata; and the interpolation logic adapts the interpolation techniquebased, at least in part, on the signal-to-noise ratio.
 8. A method,comprising: receiving a signal comprising non-pilot data that is notknown to a receiver of the signal; determining an estimated channel forthe signal based, at least in part, on the non-pilot data; processingthe signal based, at least in part, on the estimated channel to producean equalized signal; and decoding the equalized signal to produce outputdata.
 9. The method of claim 8, wherein: the signal is an OFDM signalcomprising data encoded in a plurality of data subcarriers; anddetermining the estimated signal comprises: determining asignal-to-noise ratio of data subcarriers in the output data; andestimating the channel based, at least in part, on the signal-to-noiseratio of the data subcarriers in the output data.
 10. The method ofclaim 8, wherein: the signal comprises pilot data know to the receiverof the signal; and the determining comprises determining the estimatedchannel based, at least in part, on the pilot data in the signal. 11.The method of claim 10, wherein: the determining comprises determining afirst estimated channel based on the pilot data; the processingcomprises processing the non-pilot data based, at least in part, on thefirst estimated channel to produce a first equalized signal; thedecoding comprises decoding the first equalized signal to produce firstoutput data; the determining further comprises: determining a secondestimated channel for the signal based, at least in part, on the firstoutput data; and determining the estimated channel based, at least inpart, on the first estimated channel and the second estimated channel.12. The method of claim 11, wherein: the signal is an OFDM signalcomprising data encoded in a plurality of data subcarriers; furthercomprising: determining a signal-to-noise ratio of data subcarriers inthe first output data; and estimating the channel by combining the firstestimated channel and the second estimated channel with respectiveweights based, at least in part, on the signal-to-noise ratio.
 13. Themethod of claim 11, wherein estimating the first channel comprises:adapting an interpolation technique based, at least in part, on theoutput data by i) modifying interpolation parameters, ii) selecting adifferent interpolation technique, or iii) both modifying interpolationparameters and selecting a different interpolation technique; anddetermining the first estimated channel using the adapted interpolationtechnique.
 14. The method of claim 11, wherein: the signal is an OFDMsignal comprising data encoded in a plurality of data subcarriers;further comprising: determining a signal-to-noise ratio of datasubcarriers in the first output data; adapting the interpolationtechnique based, at least in part, on the signal-to-noise ratio; anddetermining the first estimated channel using the adapted interpolationtechnique.
 15. A device comprising: a receiver circuit configured toreceive an OFDM signal comprising data encoded in a plurality of datasubcarriers; a channel estimation logic circuit configured to determinean estimated channel based, at least in part, on non-pilot data in thesignal; an equalizer circuit configured to process the signal based, atleast in part, on the estimated channel to produce an equalized signal;and a decision logic circuit configured to decode the equalized signalto produce output data; and wherein the channel estimation logic circuitis configured to: determine a signal-to-noise ratio of data subcarriersin the output data; and estimate the channel based, at least in part, onthe signal-to-noise ratio of the data subcarriers in the output data.16. The device of claim 15, wherein: the OFDM signal comprises pilotdata and non-pilot data; and the channel estimation logic circuit isconfigured to determine the estimated channel based, at least in part,on the pilot data in the signal.
 17. The device of claim 16, wherein:the channel estimation logic circuit is configured to determine a firstestimated channel based on the pilot signal components; the equalizercircuit is configured to process the non-pilot signal components based,at least in part, on the first estimated channel to produce a firstequalized signal; the decision logic circuit is configured to decode thefirst equalized signal to produce first output data; the channelestimation logic comprises a second channel estimation logic configuredto determine a second estimated channel for the signal based, at leastin part, on the first output data; and the channel estimation logicdetermines the estimated channel based, at least in part, on the firstestimated channel and the second estimated channel.
 18. The device ofclaim 17, wherein: the channel estimation logic circuit is further isconfigured to: determine respective signal-to-noise ratios of respectivedata subcarriers in the output data; and determine the estimated channelfor respective data subcarriers by combining the first estimated channeland the second estimated channel with respective weights based, at leastin part, on the signal-to-noise ratio of the respective data subcarrier.19. The device of claim 17, wherein: the channel estimation logiccircuit is further is configured to: adapt an interpolation techniquebased, at least in part, on the output data by i) modifyinginterpolation parameters, ii) selecting a different interpolationtechnique, or iii) both modifying interpolation parameters and selectinga different interpolation technique; and determine the first estimatedchannel using the selected interpolation technique.
 20. The device ofclaim 19, wherein the channel estimation logic circuit is further isconfigured to adapt the interpolation technique based, at least in part,on the signal-to-noise ratio.